Top seed Rafael Nadal made light work of Pablo Andujar at the Mexican Open in Acapulco, while Britain's Katie Boulter advanced in the women's tournament.
Nadal came through in style to win 6-3 6-2, while second seed Alexander Zverev moved past qualifier Jason Jung 7-6 (8-6) 6-1 to reach the second round.
John Isner took just over an hour to beat Mischa Zverev 6-3 7-6 (7-4), Felix Auger-Aliassime beat Australian Alex Bolt 6-3 7-6 (7-5), while there were also wins for Grigor Dimitrov, Soonwoo Kwon, Pedro Martinez, Taylor Fritz and Dusan Lajovic.
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Britain's Boulter came from one set down to beat Francesca Di Lorenzo 2-6 6-3 6-2 to advance in the WTA event.
Di Lorenzo is ranked more than 250 places higher than the 23-year-old and two consecutive breaks put the American up 4-0 as she wrapped up the first set inside 26 minutes in Acapulco.
But Boulter rallied against the lucky loser and broke the world No 120's first two service games in the second set as she forced a decider.
Again, in the third, the Briton forced two breaks early on and took a 4-0 lead and served out the set and the match to set up a tie with sixth seed Lin Zhu.
Top seed Sloane Stephens fell to home wildcard Renata Zarazua 6-4 6-2 and Venus Williams was also sent packing after a 4-6 7-6 (7-4) 6-2 loss to Kaja Juvan.
There were no such problems for sixth seed Lin Zhu, who beat Katarina Zavatska in straight sets 7-6 (7-2) 6-2, qualifier Sara Errani beat Sara Sorribes Tormo 7-5 6-4 and Leylah Annie Fernandez defeated Nina Stojanovic 6-4 6-1.
Fourth seed Lauren Davis went down 6-2 1-6 6-4 to Christina McHale and Katie Volynets saw off Shelby Rogers 6-2 7-6 (5).
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